Substitution of non-catalytic stem and loop regions of hammerhead ribozyme with DNA counterparts only increases KM without sacrificing the catalytic step (kcat): a way to improve substrate-specificity.

In elucidating structure-function relationships and stabilizing ribozymes in vivo, several chimeric RNA/DNA ribozymes and substrates were chemically synthesized. Measurements of kinetic parameters revealed that the maximally deoxyribonucleotide-substituted ribozyme (DRDRD32) gained the highest catalytic activity reaching the kcat value of > 10 min-1, the highest value ever reported for hammerhead-type ribozymes. Since these chimeric ribozymes are more stable than the wild-type all-RNA ribozymes in vivo and they also possess higher substrate-specificity, they are considered to be better candidates for antiviral therapeutic agents.